The term "polyphenylene ether resin" includes a family of polymers well known to those skilled in the art, and they are made by a variety of catalytic and non-catalytic processes from the corresponding phenols or reactive derivatives thereof. By way of illustration, certain of the polyphenylene ethers are disclosed in Hay, U.S. Pat. No. 3,306,874 and 3,306,875, and in Stamatoff, U.S. Pat. No. 3,257,357 and U.S. Pat. No. 3,257,358. In the Hay patents, the polyphenylene ethers are prepared by an oxidative coupling reaction comprising passing an oxygen-containing gas through a reaction solution of a phenol and a metal-amine complex catalyst. Other disclosures relating to processes using metal-amine catalyst are found in Bussink et al, U.S. Pat. No. 3,337,499; Blanchard et al, U.S. Pat. No. 3,219,626; Laakso et al, U.S. Pat No. 3,342,892; Borman, U.S. Pat. No. 3,344,166; Hori et al, U.S. Pat. No. 3,384,619; Faurote et al, U.S. Pat. No. 3,440,217; and disclosures relating to metal based catalysts which do not include amines, are known from patents such as Wieden et al, U.S. Pat. No. 3,442,885 (copper-amidines); Nakashio et al, U.S. Pat. No. 3,573,257 (metal-alcoholate or -phenolate); Kobayashi et al, U.S. Pat. No. 3,455,880 (cobalt chelates); and the like. In the Stamatoff patents, the polyphenylene ethers are produced by reacting the corresponding phenolate ion with an initiator, such as peroxy acid salt, an acid peroxide, a hypohalite, and the like, in the presence of a complexing agent. Disclosures relating to non-catalytic processes, such as oxidation with lead dioxide, silver oxide, etc. are described in Price et al, U.S. Pat. No. 3,382,212. All of the above-mentioned disclosures are incorporated herein by reference.
The term "alkenyl aromatic resin" includes polymers and copolymers of styrene, alpha methyl styrene, chlorostyrene, ethylvinylbenzene, divinylbenzene, vinylnaphthalene and the like.
The term "EPDM" includes rubbery interpolymers of a mixture of mono-olefins and a polyene. Preferred type are those rubbery interpolymers of ethylene, an alpha-olefin and a polyene.
In the prior art rubber-modified styrene resins have been admixed with polyphenylene ether resins to form compositions that have modified properties. The Cizek patent, U.S. Pat. No. 3,383,435 discloses rubber-modified styrene resin-polyphenylene ether resin composition wherein the rubber component is of the unsaturated type such as polymers and copolymers of butadiene. The physical properties of these compositions are such that it appears that many of the properties of the styrene resins have been upgraded, while the moldability of the polyphenylene ethers are improved.
Ger. Offen. No. 2,047,613 discloses that less than 30 by weight of an EPDM modified styrene resin may be used to upgrade the impact strength of polyphenylene ether resins. There is no suggestion to use higher amounts or that higher amounts will improve the oxidative stability and color stability of a polyphenylene ether composition.
It has now been found that when the highly unsaturated rubber that is used in compositions of the type disclosed by Cizek, is replaced with EPDM rubber that has a low degree of residual unsaturation, the thermal oxidative stability and color stability are improved.
It is, therefore, a primary object of this invention to provide improved compositions of polyphenylene ether resins and modified alkenyl aromatic resins.
Another object of this invention is to provide molding compositions and molded articles of a polyphenylene ether resin and a modified alkenyl aromatic resin which have improved thermal oxidative stability.
Still another object of this invention is to provide molding compositions and molded articles of a polyphenylene ether resin and a modified alkenyl aromatic resin which have improved color stability.
It is also an object of this invention to provide the above-described, improved molding compositions in particular embodiment that are reinforced and/or flame retardant.